Steroid metabolism: The objective is to further characterize the nature and extent of the gastrointestinal metabolism of steroids. Special attention will be given to the intracellular localization of the intestinal enzymes involved. Also their partial characterization is attempted. Studies on the phylogenetic differentation of the hepatic and intestinal metabolism will be continued. Regulation of glucuronic acid pathways: A search for a specific and harmless inhibitor of the glucuronide synthesis in living cells. Studies of the effects of the inhibitors of glucuronide synthesis in vivo both on their ability to prolong drug effects and on their pharmacological effects. The tissue specificity of inhibitors needs further clarification. The structural and functional relationship of the first and second phase (cytochrome P-450 cored system and glucuronide synthesis) in the endoplasmic reticulum membrane and the location of UDP glucuronyltransferase. The adaptation of the metabolic gradient in the glucuronide synthesis in various segments of the gut, after gastrointestinal surgery (gastrectomy, partial jejunectomy etc). Amino acid conjugation: The control mechanisms of the amino acid conjugation, the effect of substrate administration and age. The fate of different substrates in different species. Comparison of pulmonary metabolic function with the gastrointestinal steroid metabolism.